HORIBA Scientific announces an innovative filtering technology for Ultralow Frequency Raman measurements
Raman spectroscopy has gained an established reputation in providing chemical and structural identification quickly and reliably. With the recent introduction of the ULF module in the LabRAM HR series, HORIBA Scientific has expanded the working range of its benchtop Raman microscopes providing access to ultralow frequency (ULF) modes below 50 cm-1. Low-frequency modes can give detail on conformational changes, subtle changes in lattice structure and microcrystallites size and reveal key information for the structural investigations of pharmaceutical polymorphs, LA modes in polymers and superlattice modes of semiconductor materials.
With the new ULF module, spectro-scopic information as low as 10 cm-1 is readily available, opening up new areas of research for routine Raman microscopy and is no longer confined to large research systems or complex and expensive instruments such far IR or terahertz spectrometers.
Horiba has recently demonstrated the use of a single monochromator Raman system where the Rayleigh filtering elements are made of volume Bragg gratings for the recording of Stokes and anti-Stokes modes with frequencies of less than 10 cm-1. Such filters exhibit a very narrow bandwidth of less than 10 cm-1, which is about 30 to 40 times narrower than other notch and bandpass filters commercially available for these applications today and show outstanding environmental stability, with no humidity or light-induced degradation, and can withstand temperatures up to 450°C.
The initial results presented at the International Conference for Raman Spectroscopy (ICORS) in Boston, MA, USA, in August 2010, demonstrated the feasibility of measuring Stokes and Anti-Stokes frequencies down to 4.5 cm-1. The Horiba’s new Ultra Low Frequency Unit with BragGrate (Optigrate Corp.) filters is now available for a wide range of Raman laser wavelengths such as 488, 514, 532, 633, 785, and 1064 nm. For more information, please go to: www.horiba.com/scientific.
Figure Caption: SiGe superlattice Raman spectrum at low frequency exhibiting both Stokes and anti-Stokes features recorded with the new ULF option at 633 nm. Sample courtesy of P. H. Tan, State Key Laboratory for SL and Microstr., Institute of Semiconductors, Beijing, P. R. China, and K. Brunner, University Wurzburg, Germany
